This proposal concerns studies of the retina as a model system of a neural tissue and for the study of biochemical control. Glutamine Synthetase (GS) and other enzymes, and their possible relation to vision as well as general retinal metabolism and drug effects are a major focus. PREVIOUS STUDIES HAVE SHOWN: 1) structual requirements of steroid for GS induction 2) improved GS assay 3) GS induction in retinoblastoma-derived cells 4) that GS is not confined to a single retinal cell type; 5) enhancement of cortisol induction of GS by Actinomycin-D 6) normal early development of GS in retinas of mice with inherited retinal dystrophy 7) effects of glutamine and glutamate on GS and on retinal morphology 8) continued increase of GS after wash-out of inducer 9) uptake of hormone by retina decreases in older embryos. CURRENT STUDIES CONCERN: 1) mechanism of action of glutamate and related compounds in the retina, and in people 2) other metabolic phenomena in the retina including drug effects 3) role of tissue integrity in normal functioning of GS control mechanisms 4) intracellular site of action of cortisol and amino acids which appear to control GS 5) possible roles of cations and other serum factors in the control mechanisms of normal and diseased retinas 6) examination of other enzyme activities in developing retinas 7) how some of the aforementioned may relate to the visual cycle or to known retinal abnormalities. METHODS INCLUDE: 1) use of tissue and cell culture as well as in ovo experiments 2) radioactive tracer methods 3) use of metabolic inhibitors 4) light microscopic evaluations of morphological changes caused by some materials which give rise to biochemical changes 5) gel electrophoresis 6) column chromatography 7) millipore filter binding techniques.